Method of lift-off microstructuring deposition material on a substrate, substrates obtainable by the method, and use thereof

ABSTRACT

Methods and apparatus for lift-off microstructuring deposition material, here alternate hydrophilic ( 601 ) and hydrophobic ( 602 ) letters, on a substrate; a method comprising deposition of polymeric material by plasma polymerisation deposition of monomers of substituted benzenes, (halo)aliphatic compounds, or a combination thereof; another method comprising deposition of polymeric material by plasma polymerisation deposition of monomers of vinyls, substituted vinyls, acrylics, silanes, and phosphites, or a combination thereof; still another method comprising deposition of polymeric material by plasma polymerisation deposition of monomers wherein said plasma is generated by a multiple phase AC supply, or DC supply; and substrates and devices prepared by lift-off microstructuring using plasma polymerisation deposition of monomers according to such methods. Scale A indicates about 100μ.

BACKGROUND OF THE INVENTION

The present invention relates to methods of lift-off microstructuringdeposition material on a substrate; a method comprises deposition ofpolymeric material by plasma polymerisation deposition of monomers ofsubstituted benzenes and (halo)aliphatic compounds; another methodcomprises deposition of polymeric material by plasma polymerisationdeposition of monomers wherein said plasma is generated by a multiplephase AC supply, or DC supply; and substrates and devices prepared byplasma polymerisation deposition of monomers according to such methods.

1. The Technical Field

In cell-based drug screening, the methods used today are usually tediousand labour consuming. Electrical measurements are typically conducted onsingle cells under microscope. Here, microelectrodes are positioned onthe individual cells manually using micro-manipulators. The cells arethen exposed to different drugs, one at a time, and the potential orconductivity etc. is measured. In the case of optical measurements, forinstance fluorescence, a cluster of cells producing fluorescent proteinsare placed in a flow cell. The drug is introduced to the cluster througha flow system, and the fluorescence they produce is detected using afluorescence microscope.

In today's High Throughput Screening (HTS), optical screening is usuallyconducted by steps comprising dispensing cells, using a dispenser robot,into an array of wells on a transparent microtiter plate. Next, a set orsets of drugs, e.g. drugs mixed on-site, is dispensed into the wells,and optical measurements are performed. Detectors are typically placedover the microtiter plate and light sources underneath. One advantagesof this technique is the fact that it is highly automated and a numberof drugs can be screened simultaneously.

Disadvantages include the fact that larger number of cells and largevolumes of drugs (typically from a couple of microliters) are needed inorder to do the measurements. Also, the dimensions of the wells limitthe number of measuring sites in the array.

Lift-off microstructuring is a technique for providing micro-structureddevices, including substrates having microstructured deposition materialthereon, said deposition material e.g. being polymeric material ormetal. It includes the step of providing a substrate with a sacrificiallayer, said sacrificial layer having a predetermined micro-patterncomplementary to that of the desirable micro-pattern of the depositionmaterial.

After deposition of the deposition material, the sacrificial layer withdeposit thereon is removed, either mechanically or chemically, e.g. bydissolution/etching. In the specific shadow mask lift-off technique, thesacrificial layer constitutes a mask containing said complementarydesired pattern. The deposition material is normally deposited in such amanner that it covers the parts of the substrate, which are not coveredby the sacrificial layer as well as the parts of the substrate alreadycovered by the sacrificial layer. When the sacrificial layer is removed,e.g. dissolved/etched, a micro-pattern of the deposit material that iscomplementary to the pattern of the sacrificial layer is revealed.

The term sacrificial layer is intended to cover conventional materialsused in micro-patterning deposition of semiconductor devices by lift-offmicro-structuring e.g. photo-resists, metals, oxides, ceramics, polymersetc.

There is a need for an improved and more flexible lift-offmicro-structuring method and apparatus in which strongly bindingdeposition materials, including polymers, in particular polymers withdifferent surface properties, can be provided on the same substrate.

2. Prior Art Disclosures

Y. Pan et al., “A Precision Technology For Controlling ProteinAdsorption And Cell Adhesion In Biomems”, MEMS'01, “The 14th IEEEInternational Conference on Micro Electro Mechanical Systems”, pages435-438, 21-25 Jan. 2001, Interlaken, Switzerland, describe a lift-offprocess for microstructuring plasma polymerised tetraglyme (pp4G)deposit on a silicon wafer using RF plasma having plasma power densitieswhich to a large extent decomposes ether bonds. The polymerisedtetraglyme provides cell non-adhesive surfaces on the surface.

U.S. Pat. No. 4,371,407 discloses a plasma polymerisation method usingRF plasma of plasma power densities above 20 W/l for deposition of CF₄,C₂F₆, C₃F₈ in mixture with H₂, i.e. saturated fluorocarbon whichrequires high plasma power densities for plasma polarisation.

EP 0 741 404 B1 discloses a method and an electrode system forexcitation of a plasma.

WO 00/20656 discloses a method of metallizing a surface of a solidsubstrate.

WO 00/44207 discloses a method of excitation of a plasma by means of aplurality of electrode systems.

C. H. Thomas et al., Transactions of the ASME, Vol. 121, 1999, disclosesa process for the preparation of a substrate on which single cells canbe isolated on isolated patches of amino-terminated silane surrounded bya non-adhesive hydrogel of acrylamide and polyethyleneglycol.

U.S. Pat. No. 5,470,739 discloses a process for providing a patterneddesign useful as a cell culture support. Patches of the surface arecoated with collagen which influences cell-adhesion.

2. DISCLOSURE OF THE INVENTION

Object of the Invention

It is an object of the present invention to seek to provide an improvedmethod and apparatus for microstructuring deposition material on asubstrate, in particular lift-off microstructuring.

It is an object of the present invention to seek to provide such amethod and apparatus whereby deposition material comprising multiplepolymer surfaces can be provided on the same substrate.

It is a further object of the present invention to seek to provide sucha method and apparatus which allow a substantial portion of functionalgroups on monomers for said polymers to be preserved.

Further objects appear from the description elsewhere.

Solution According to the Invention

“Lift-Off Microstructuring—Plasma Polymerisation Deposition ofSubstituted Benzene and (Halo)Aliphatic Compounds”

In an aspect according to the present invention, these objects arefulfilled by providing a method of lift-off microstructuring adeposition material on a substrate as defined in claim 1, the methodcomprising:

-   (a) providing the substrate having a sacrificial layer in a    predetermined micro-pattern;-   (b) depositing a polymer layer on the sacrificial layer/substrate;-   (c) dissolving/etching the underlying sacrificial layer (lift-off),    characterised in that the polymer layer is constituted by a    cross-linked polymeric material prepared by plasma polymerisation of    a monomer gas in a plasma, said monomer gas comprising one or more    types of monomers selected from-   (i) substituted benzenes, and-   (ii) (halo)aliphatic compounds of the general formula    C_(z)H_(y)X_(x) wherein X is fluoro, 15 chloro, bromo or iodo, z is    1-16 and x+y is 2z+2, 2z, 2z-2 or 2z-4;    with the proviso that said (halo)aliphatic compounds are not CF₄,    C₂F₆, or C₃F₈.

It has surprisingly turned out that for such a micro-structuring methodwherein said deposition of a deposition material on said sacrificiallayer comprises a plasma polymerisation deposition of a monomer gas,said monomer gas being comprising one or more types of monomers selectedfrom said substituted benzenes, and (halo)aliphatic compounds; with theproviso that said (halo)aliphatic compounds are not CF₄, C₂F₆, or C₃F₈;it is obtained that substrates with microstructured deposition materialof low feature sizes, multiple polymer surfaces with accurate alignment,and deposited polymers having functional groups which are sensitive tohigh plasma power densities can be provided.

Preferred embodiments are defined in the sub claims.

“Monomers—Substituted Benzenes”

In an aspect, lift-off microstructuring comprises plasma polymerisationdeposition of a monomer gas comprising one or more types of monomersselected from substituted benzenes.

The substituted benzenes may—as a matter of definition—have 1-6substituents, but will most often have 1-4 substituents, preferably 2-4substituents, in particular 2-3 substituents.

It is believed that preferred substituted benzenes are those which haveno polymerisable groups such as alkenyl, alkynyl, etc. substituents.

Examples of suitable substituted benzene monomers have the generalformula:Ar(R^(n))_(n)wherein Ar is a benzene ring, n is 1-6 and Rn is n substituents R¹, R²,R³, R⁴, R⁵R⁶ covalently bound to the benzene ring, the substituents R¹,R², R³R⁴, R⁵, R⁶ being independently selected from: C₁₋₆-alkyl,C₁₋₆-alkenyl, C₁₋₆-alkynyl, C₁₋₆-alkoxy, C₁₋₆-alkylcarbonyl,C₁₋₆-alkylcarbonyl, C₁₋₆-alkoxycarbonyl, carbamoyl, mono- anddi(C₁₋₆-alkyl)-aminocarbonyl, formyl, hydroxy, carboxy, carbamido,thiolo, nitro, cyano, nitro, amino, mono- and di(C₁₋₆-alkyl)amino, andhalogen (fluoro, chloro, iodo, bromo), wherein the C₁₋₆-alkyl,C₁₋₆-alkenyl, C₁₋₆-alkynyl and C₁₋₆-alkoxy groups in the above may besubstituted with substituents, preferably 1-3 substituents, selectedfrom hydroxy, C₁₋₆-alkoxy, carboxy, amino, mono- and di(C₁₋₆-alkyl)aminoand halogen.

In the formula above, it is preferred that the substituents are selectedfrom C₁₋₂-alkyl, amino, and halogen.

Particular examples of suitable substituted benzenes are p-xylene,m-xylene, o-xylene, omethylaniline, m-methylaniline,2,3-dimethylaniline, 2,4-dimethylaniline, 2,5-dimethylaniline,2,6-dimethylaniline, 3,5-dimethylaniline, fluorobenzene, etc.

“Examples of further benzene monomers: toluene, xylene, benzaldehyde,chlorobenzene, di-chlorobenzene, trifluorobenzene.”

Particularly useful substituted benzenes are those having two or moresubstituents where one substituent is a methyl group.

Also preferred are benzenes which do not include alkenyl or alkynylsubstituents.

Preferred substituted benzenes are those having at least twosubstituents.

This being said, it is believed that particularly useful substitutedbenzenes are those which do not include oxygen atoms. This isparticularly true when the substrate is silicon-containing in that anyformation of Si—O—C bonds (which may be susceptible to hydrolysis withstrong bases) between the oxygen atom of the substituted benzene andsilicon atoms of the substrate is thereby avoided. Preferably less than5 mol-% of the monomers of the substituted benzene type comprises oxygenatoms.

As will be obvious from the above, the monomer gas may comprise othermonomer types than the substituted benzene monomers. In order to fullybenefit from the advantageous properties provided with the substitutedbenzene monomers, it is believed that the content of substituted benzenemonomers, should be at least 5 mol %, although the content can be evenhigher such as in the range of 10-100 mol-%, e.g. 25-100 mol-%, such as75-100 mol-%, and often about 100 mol-%.

The amount defined for the substituted benzenes may encompass one or twoor more different substituted benzenes, normally however, only one isused or two are used together.

As mentioned above, it has been found that the double bonds originatingfrom the benzene structure often are virtually absent in the polymericmaterial prepared from the substituted benzenes. This being said, thematerials will generally have less than 20% of the double bondsoriginating from the benzene structure of the substituted benzenes left.Typically as little as less than 10% of the double bond, preferably lessthan 5%, of the double bonds originating from the benzene structure ofthe substituted benzenes are left. This appears to be an importantcharacteristic of the materials of the present invention.

The amount of double bonds left can be determined by FT-IR measurementor by reaction with bromine or fluoro-compounds followed by elementalanalysis with EPS (X-ray Photoelektron Spectroscopy).

“Monomers—Substituted (Halo)Aliphatic Compounds”

In another embodiment, said cross-linked polymer may also be providedwith a (halo)aliphatic compound of the general formula C_(z)H_(y)X_(x)wherein X is fluoro, chloro, bromo or iodo, z is 1-16. The number ofsubstituents, i.e. the sum x+y, is 2z+2, 2z, 2z-2 or 2z-4 correspondingto straight chain (halo)aliphatic compounds, (halo)cycloaliphaticcompound or monounsaturated (halo)aliphatic compounds, anddi-unsaturated (halo)aliphatic compounds or mono unsaturated(halo)cycloaliphatic compounds, etc., respectively.

The term “(halo)aliphatic compound” is intended to mean an aliphaticcompound 30 optionally being substituted one or more times with fluoro,chloro, bromo or iodo, preferably fluoro or chloro, such asperhalogenated compounds.

Examples of preferred (halo)aliphatic monomers for the process of theinvention are:

-   a) Alkynes: HC≡CH, HC≡C—(CH₂)_(r)—CH₃ (0≦r≦14).-   b) Alkenes: H₂C═CH₂ and H₂C═CH—(CH₂)_(r)—CH₃ (0≦r≦14) and cyclic    alkenes.-   c) Alkanes: CH₄, CH3—(CH₂)_(r)—CH₃ (0≦r≦14) and cyclic alkanes.-   d) Haloalipatics: Monomers from group a, b and c containing one or    more halogen atoms (F, Cl, Br and I).

The compounds can be utilised either in combination with the substitutedbenzenes or alone. The (halo)aliphatic compounds provides in themselveshydrophobic surface properties upon plasma polymerisation.

Examples of fully or partially halogenated organic compounds(haloaliphatic compounds) are perfluorocyclohexane, perfluorohexane,perfluoromethylpentene, difluoroethylene, etc.

When the (halo)aliphatic compounds are used, it is believed that thecontent of (halo)aliphatic monomers should be at least 5 mol-%, althoughthe content can be even higher such as in the range of 10-100 mol-%,e.g. 25-100 mol-%, such as 75-100 mol-%, and often about 100 mol-%. Inone embodiment, the (halo)aliphatic compounds are used in combinationwith the substituted benzenes.

“Other Monomers”

Other types of monomers can be used as the balance in the monomer gas inorder to modify the properties of the materials. Such other types ofmonomer may be provided either by preparing a mixture of monomers to beapplied simultaneous or by providing alternating amounts of differentmonomer types so as to form a virtual mixture in the plasma environment.

Illustrative examples of other monomer types to be selected fromvinylacetate, vinylpyrrolidone, ethyleneglycolvinylether,diethyleneglycolvinylether, methyl methacrylate, methyl methacrylate,allylalcohol, vinylbornene, acid anhydrides (in particular carboxylicacid anhydrides), acid halides (in particular carboxylic acid halides)such as acid chlorides, acid bromides, acid fluorides, acid iodides,epoxides, aldehydes, carboxylic acids, and thiols. In addition to themonomers above, the monomer gas may also comprise gaseous monomers suchas NH₃, N₂, N₂O, CO₂, etc.

Examples of benzene monomers: toluene, xylene, benzaldehyde,chlorobenzene, di-chlorobenzene, tri-fluorobenzene.

“Lift-Off Microstructuring—Plasma Polymerisation Deposition of OtherMonomers—Vinyls, Substituted Vinyls, and Acrylics”

In an aspect according to the present invention, these objects arefulfilled by providing a method of lift-off microstructuring adeposition material on a substrate as defined in claim 13, the methodcomprising:

A method of lift-off microstructuring of a polymer on a substrate, saidmethod comprising the steps of:

-   (a) providing the substrate having a sacrificial layer in a    predetermined micro-pattern;-   (b) depositing a polymer layer on the sacrificial layer/substrate;-   (c) dissolving/etching the underlying sacrificial layer (lift-off),    characterised in that the polymer layer is constituted by a    cross-linked polymeric material prepared by plasma polymerisation of    a monomer gas in a plasma, said monomer gas comprising one or more    types of monomers selected from: vinyls, substituted vinyls,    acrylics, silanes, and phosphites, or a combination thereof.

Among monomers, preferred monomers comprises at least one polymerisablegroup which forms the polymer backbone of the plasma polymeriseddeposition or coating, and at least one functional group which ispreserved during the plasma deposition and which is bound to the polymerbackbone.

In traditional liquid phase polymerisation, e.g. free radicalpolymerisation, the most common polymerisable groups are vinyls,substituted vinyls, and acrylics. Said polymerisable groups are alsosuited for plasma polymerisation, and polymerise at very low plasmapower densities. Low plasma power densities at the same time allow forpreservation of the functional group.

Furthermore, plasma technology allows for the use of a large number ofpolymerisable groups. In fact, nearly any organic compounds may bepolymerised in a plasma process. The more inert the group is the higherthe required plasma density. However, the higher the plasma powerdensity, the less is the probability that the functional group ispreserved. Examples of plasma polymerisable groups which can bepolymerised at conveniently low plasma power density are benzenes,silanes, and triphosphites.

In conclusion preferred examples of said polymerisable group P areacrylics, vinyls, benzenes, silanes, and triphosphites.

Examples of acrylic monomers: acrylic acid, methylmethacrylate,acrolein, acryloylchloride, acrylonitrile.

Examples of vinyl monomers: ethylene, propylene, styrene,N-vinylpyrrolidone.

Examples of substituted vinyl monomers: vinyl-di-fluoride,hexafluoropropane, vinylchloride.

“Other Monomers—Silanes and Phosphites”

Examples of silane monomers: tetramethylsilane, hexamethyl-di-silane,tri-methylchlorosilane.

Examples of tri-phosphites: tri-methyl-phosphite, triethyl-phosphite.

“Lift-Off Microstructuring—Plasma Polymerisation Deposition Using LowPlasma Power Density”

In another aspect according to the present invention, these objects arefulfilled by providing a method of lift-off microstructuring adeposition material on a substrate as defined in claim 26, the methodcomprising:

-   (a) providing the substrate, the substrate comprising a sacrificial    layer thereon, said sacrificial layer having a predetermined    micro-pattern;-   (b) depositing the deposition material on the substrate and said    sacrificial layer; and-   (c) dissolving/etching said sacrificial layer,    wherein said deposition material is polymer constituted by a    cross-linked polymeric material prepared by plasma polymerisation of    a monomer gas in a plasma, said plasma being generated by a multiple    phase AC supply or DC supply.

It has surprisingly turned out that for such a micro-structuring methodwherein said deposition of a deposition material on said sacrificiallayer comprises a plasma polymerisation deposition of a monomer gas,said monomer gas being comprising one or more types of monomers,selecting a plasma which is provided by a multiple phase AC supply or DCsupply ensures a plasma of a level of intensity which allows asubstantial portion of the functional groups of the monomer of to bepreserved.

Preferred embodiments are defined in the sub claims.

It is particularly advantageous to utilise two-phase or three-phase ACplasma which offers the possibility of using a sufficiently low energy,e.g. energy levels of at the most 15 W/l such as at the most 10 W/l.

In a preferred embodiment, said plasma being generated by a two or threephase AC supply.

In a preferred embodiment, said two or three phase AC supply generatesplasma having a plasma power density up to 15 W/l, preferably in therange 0.010 to 10 W/l, in particular 0.010 to 5 W/l.

This type of plasma has a level of plasma power density which allows asubstantial portion of the functional groups to be preserved wherebymonomers having specific functional group can be used formicro-structuring polymers containing such groups on the substrate.

In a preferred embodiment, said monomer gas comprises one or more typesof monomers selected from

-   (i) substituted benzenes, and-   (ii) (halo)aliphatic compounds of the general formula    C_(z)H_(y)X_(x) wherein X is fluoro, chloro, bromo or iodo, z is    1-16 and x+y is 2z+2, 2z, 2z-2 or 2z-4.

In another embodiment, said monomer gas comprises one or more types ofmonomers selected from: vinyls, substituted vinyls, acrylics, silanes,and phosphites, or a combination thereof.

The present invention also provides a substrate prepared according tothe process.

“Plasma Polymerisation Deposition”

The plasma type advantageously used in the concept of the presentinvention is typically one generated by a multiple phase AC supply or aDC supply.

It has been found that this type of plasma has a level of plasma powerdensity which allows a substantial portion of the functional groups tobe preserved.

It is particularly advantageous to utilise two or three phase AC plasmawhich offers the possibility of using a sufficiently low plasma powerdensity, e.g. plasma power density of at the most 15 W/l such as at themost 10 W/l.

Preferably, the plasma power density of the plasma is in the range of 10mW/1 to 15 W/l, such as 10 W/l to 10 W/l, e.g. 10 mW/1 to 5 W/l.

Other types of generators of the plasma may also be applicable, e.g. RFand MF plasma and pulsed variants thereof, in particular for less energysensitive functional groups of the monomers.

The pressure in the reaction chamber will normally be in the range of10-1000 μbar, such as 25-500 μbar.

The pressure in the reaction chamber is controlled by a vacuum pump, anda supply of an inert gas and the monomer gas. The inert gas is suitablya noble gas such as helium, argon, neon, krypton or a mixture thereof.

Hence, a plasma reaction chamber can be adapted in accordance with theinstructions given herein with possible modification obvious for theperson skilled in the art.

The plasma polymerisation process is normally conducted for a period of10-1000 s, 20 such as 20-500 s.

The plasma-polymerised material can be provided on the substrate in asubstantially uniform thickness if desired. It is believed that thelayer thickness of the material generally is in the range of 5-5000 nm,such as in the range of 10-1000 nm, typically 10-200 nm.

“Substrates”

A wide range of substrates are suitable in the method of the invention,thus typically the solid substrate essentially consists of a materialselected from polymers, e.g. polyolefins such as polyethylene (PE) andpolypropylene (PP), polystyrene (PS), or other thermoplastics such aspolytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylencopolymers (FEP), polyvinyl-difluoride (PVDF), polyamides (e.g.nylon-6.6 and nylon-11), and polyvinylchloride (PVC), rubbers e.g.silicone rubbers, glass, silicon, paper, carbon fibres, ceramics,metals, etc.

Presently preferred materials are silicon, polyethylene (PE),polystyrene (PS) and glass, of which silicon is particularly interestingin view of the particularly useful products for micro-structuringlift-off techniques.

If the substrate is not supplied with sufficiently clean andready-to-use surfaces, one or more initial cleaning treatments may beneeded. Such cleaning treatments often depend on the substrate and areknown in the art.

“Pre-Coated Substrates and Sacrificial Layer”

The substrate (and sacrificial layer) may be pre-coated or pre-treatedin order to modify the properties thereof, e.g. the ability of thesurface to adhere to the plasma polymerised material, or the hydrophobicor hydrophilic properties of the substrate as such. The pre-coating may(also) be performed by plasma polymerisation. In the case where thesubstrate is silicon, it is preferred that the surface therefore ispre-treated with a hydrogen plasma before the material is provided ontothe silicon in that occasional Si—OH groups are thereby converted toSi—H groups. This step can be performed as a pre-step to the step ofproviding the polymer layer (see Example 1). Also interesting ispre-treatment with argon so as to clean and possibly activates thesurface prior to plasma polymerisation with the substituted benzene.

The surface properties of the polymer is determined by the substitutedbenzenes and/or (halo)aliphatic compounds used in the plasmapolymerisation process, as well as by any additional monomers used asthe balance of the monomer gas.

Besides the fact that the polymer in itself may provide specific surfaceproperties, it is also possible to modify the surface properties of thepolymer even before the sacrificial layer is dissolved/etched.

As will be understood, hydrophobic, hydrophilic, cell-adhesive and cellnon-adhesive surface properties of predefined patches (defined by themicro-pattern) for the substrate may be provided either by mixingsuitable monomers with the substituted benzenes or may provided byplasma polymerisation of a further layer on top of the cross-linkedmaterial (plasma polymerised monomer gas comprising substitutedbenzenes).

One advantage of the present process resides in the fact that theplasma-polymerised substituted benzenes provide a durable cross-linkedmaterial which has a strong bonding to the substrate (and thesacrificial layer). It is therefore possible to manipulate the substrateand to provide further layers without affecting the integrity of thepattern provided with the cross-linked material (and optional furtherlayers on top thereof).

Thus, the surface properties can be provided by the monomer gas as such;by components provided by plasma polymerisation in succession of plasmapolymerisation of the monomer gas; or by “wet” chemical modification ofthe polymer surface, e.g. initially prepared by plasma polymerisation.

In one important embodiment, the polymer layer is functionalised priorto dissolution (or etching) of the underlying sacrificial layer.

The monomer gas as such can provide either a hydrophobic surface, i.e.when substituted benzenes with substituents other than amino, mono- anddi(C₁₋₆-alkyl)amino, thiolo and hydroxyl are used and when the(halo)aliphatic compounds are used, or a hydrophilic surface, i.e. whensubstituted benzenes with amino, mono- and di(C₁₋₆-alkyl)amino, thioloand hydroxyl substituents are used.

As it is illustrated in the examples, a further plasma polymerised layermay be provided on top of the material defined above. Such a layer mayprovide modify the surface properties of the polymer and may providespecial surface properties to the material, e.g. hydrophobicity,hydrophilicity, cell-adhesive surface property, cell-repellenceproperties, etc.

The further plasma polymerised layer may be provided in directsuccession of the polymer layer, i.e. as in illustrated in Example 2where the monomer gas containing the substituted benzene is turned offafter which the 1-vinyl-2-pyrolidone monomer is provided. This directsuccession of monomers provides a very strong bonding between the twolayers.

Alternatively, the further plasma polymerised layer may be provided in aseparate process.

In the process of preparing the cross-linked materials it is possible toadd a monomer which provides hydrophilic properties eithersimultaneously with plasma polymerisation of substituted benzene orsubsequent to plasma polymerisation of substituted benzene (see Example2). Examples of monomers which can be combined with substituted benzenesor which can be polymerised in a subsequent step are acrylic acid,vinylacetate, ethanol, ethylenediamine, allylamine, vinylpyrolidone,vinylaniline, imidazoles such as vinylimidazole, or a mixture ofacetylene and N₂O, etc.

When used herein, the term “cell non-adhesive surface” is intended torefer to a non-adhesive surfaces with regards to cells, i.e. a surfacewhich prevents bio-fouling.

Examples of monomers which in combination with substituted benzenes orin a subsequent step provides a cell non-adhesive surface arepolyethyleneglycols and derivatives, e.g. triethyleneglycol (“triglym”)and diethylene-glycol-vinylether (DEGVE), as well as silicone monomers,e.g. hexamethylcyclotrisiloxane (D3).

When used herein, the term “cell-adhesive surface” is intended to referto a surface with predominant adhesion to cells, i.e. a surface whichpromotes cell-attachment.

Examples of monomers which provides a cell-adhesive surface area areacid and/or base groups, e.g. acrylic acid and allylamine,vinyldifluoride, and the like.

Thus in one embodiment, the invention provides a substrate with ahydrophilic surface.

In another embodiment, the invention provides a substrate with ahydrophobic surface.

In a further embodiment, the invention provides a substrate with acell-adhesive surface.

In a still further embodiment, the invention provides a substrate with acell non-adhesive surface.

In an even still further embodiment, the invention provides a substratewith a surface which is either:

-   hydrophilic and cell-adhesive,-   hydrophilic and cell non-adhesive,-   hydrophobic and cell-adhesive, or-   hydrophobic and cell non-adhesive.

Thus, the substrate may have a surface which has more than onefunctionality. This makes it possible to accurately design the surfaceto, e.g., discriminate between various types of cells.

The various surface properties can also be provided by “wet” chemicalprocess. As an example, conducting surfaces may be provided in asubsequent step, i.e. after polymerisation of the substituted benzene(and other monomers), by means of combinations of monomers andconstituents already known in the art, e.g. electro30 polymerisation ofpyrrole (see, e.g., “Preparation and Characterisation of ProcessableElectroactive Materials, Anders Ravn Sorensen, Ph.D. Thesis, July 1993,ATV

Erhvervsforskerprojekt EP 336, Denmark) and sputtering of metals, e.g.platinum, in thin (1-100 nm) layers, and subsequent electrochemicalmethod for the preparation of thick (0.5-10 μm) metal layers, e.g.copper layers.

Furthermore, “wet” chemical modification of the surface of the plasmapolymerised polymer may also involve reaction with any functional groupsof the polymer, e.g. amino groups, etc. so as to attach entities withspecific affinity for biomolecules, e.g. proteins, cells, DNA, RNA, PNA,LNA, etc.

“Medical Devices and Bio-Devices”

In another aspect according to the present invention, these objects arefulfilled by providing medical devices or bio-devices on which aplurality of patches or areas is provided by lift-off microstructuringaccording to the present invention.

In a preferred embodiment, a device comprising a micropatternedstructure, said device comprising a substrate and a plurality of patchesand/or areas comprising a cross-linked material prepared by plasmapolymerisation deposition of a monomer gas in a plasma, said monomer gascomprising one or more types of monomers, preferably said type of plasmahaving a sufficient low plasma power density, said monomer beingselected from

-   (i) substituted benzenes, and    -   (ii) (halo)aliphatic compounds of the general formula        C_(z)H_(y)X_(x) wherein X is fluoro, 15 chloro, bromo or iodo, z        is 1-16 and x+y is 2z+2, 2z, 2z-2 or 2z-4.

In one embodiment, the process steps are repeated two, three or moretimes whereby patches having different surface properties can beprovided on the same substrate.

In particular, this makes it possible to provide a device, wherein theplurality of patches comprising the cross-linked material represents anyof the following combinations of surface properties:

-   (i) a subset of the patches and/or areas having a cell non-adhesive    surface and a subset of the patches and/or areas having a    cell-adhesive surface;-   (ii) a subset of the patches and/or areas having a cell-adhesive    surface and a subset of the patches and/or areas having a    hydrophobic surface;-   (iii) a subset of the patches and/or areas having a cell    non-adhesive surface and a subset of the patches and/or areas having    a hydrophobic surface;-   (iv) a subset of the patches and/or areas having a cell-adhesive    surface and a subset of the patches and/or areas having a    hydrophilic surface; or-   (v) a subset of the patches and/or areas having a cell non-adhesive    surface and a subset of the patches and/or areas having a    hydrophilic surface.    “Industrial Uses”

The material has proven particularly useful for providing toughcross-linked layers for the present micropatterning processes where thelift-off technique is utilised. The lift-off technique requires that thematerials used can resist treatment with strong solvents such asacetone, toluene, dichloroethylene, THF, etc. or strong alkalineconditions such as NaOH solutions at pH 14, etc. As will be evident fromExample 4, the cross-linked materials provided with the plasmapolymerisation of substituted benzenes are extremely useful for lift-offprocesses.

Some important applications of the invention are believed to bediagnostics or drug discovery. These applications often require somesort of manipulation, immobilisation or positioning of biologicalentities such as cells, or liquids such as regents and drugs.

In cell-based screening, it is very desirable to be able toautomatically position cells in an array and apply different testliquids to the cells—possibly fully integrated in a bio microchip.

Two possible schemes include: firstly, an array with small cell-adhesivesurface patches, typically below 5 μm in diameter, where the cells areattached. The cell-adhesive surface patches are surrounded by a cellnon-adhesive surface area, which prevents cell-attachment. Cells usuallyhave high affinity to almost all surfaces. By deposition a polymer withsuitable surface properties, for instance polyethylene glycol (PEG) orplasma-polymerised tetraglyme (pp4G), this can be prevented effectively(Y. Pan et al., 435-438, MEMS'2001).

Secondly, in a more elaborate scheme, test liquids are positioned on topof the cells. Small cell-adhesive surface patches are surrounded bysmall hydrophilic patches, which in turn are surrounded by a hydrophobicarea. The liquids are applied onto the hydrophilic area using a standardmicro dispenser. The surrounding highly hydrophobic area constrains theliquids and cells to the small measuring sites. Separate measurements,either electrical or optical can then be conducted. Fluorescencemeasurement is an especially interesting application, since it is widelyused in cell-screening. Detectors could be placed over the measuringsites and a light source underneath. This however requires a transparentsubstrate such as glass instead of silicon.

In the case of electrical measurements, different electrodes, forinstance AgCl, Au, Pt, etc. and different electrode configurations maybe used. Electrodes can be located at each measuring point or whereveron the substrate.

Thus, the present invention has the potential of making especially thetedious electrical measurement methods obsolete, since it is a more orless fully automated array, which can screen a large number of drugssimultaneously. The main advantages of the present invention compared tooptical HTS is, that single cell measurements are possible and that muchsmaller drug volumes (nanoliter range) are needed. Also, since the areaof each measuring point is much smaller than that of the conventionalHTS, a much bigger array per area is possible. The measurement procedureis very similar to the one described further above. It could be asfollows: Cell suspension is dispensed over the measuring points in thearray using a micro-dispenser. The small cell-adhesive surface patchesfixate single cells. The rest of the cells are sucked away through holesin the substrate or by flushing the surface. Next, a set or sets ofdrugs are dispensed over the measuring points and the measurement isconducted. When the measurement is finished, the drugs are removed and aset of new drugs may be dispensed and new measurements are performed.

Particular applications which can be envisaged for the products of thepresent invention are:

1. Conducting circuits for micro sensors, in particular for environmentsof harsh chemical exposure.

a. Micro sensors for the chemical industry, organic synthesis andanalytical purposes, e.g. pH measurements, measurement of ionicstrength, and measurement of salt concentrations.

b. Micro sensors for biotechnological purposes, including sensors forimplantation in living organisms (such as humans), e.g. sensors formeasurement of blood sugar in diabetic patients, sensors formeasurement/registration of nerve pulses (e.g. in muscles, skin, brain,spinal marrow) and sensors for measurement of conductivity in micro flowsystems.

2. Conducting circuits for micro actuators, in particular forenvironments of harsh chemical exposure, and for biotechnologicalpurposes including sensors for implantation in living organisms (such ashumans).

a. Actuators for stimulation of nerves in living organisms e.g. inmuscles, skin, brain, spinal marrow.

b. Actuators for controlling mechanical units, e.g. dosage pumps, inliving organisms and in micro flow systems.

3. Conducting structures for establishing voltage fields which render itpossible to control movement and/or fixation of, e.g., biomolecules suchas cells and proteins by utilising the inherent charge of such moleculesin combination with the applied voltage in the conducting structure.

a. Conducting structures for micro electrophoresis b. Conductingstructures for movement and fixation of cells and other biomolecules inmicro flow systems.

4. Conducting circuits for electronic components.

5. Optically active/non-optically active structures or structures wherevarious parts have different optical properties.

Designations and Expressions

In the present context, it is intended that the expression“microstructuring” has a similar meaning as the term “micropatterning”.

The expression for various frequencies of a plasma have the followingmeanings: DC: 0 Hz, AC: 1 Hz to 10 kHz, RF: 13.45 MHz, and MF: about 2.6GHz.

Generally, the expression “hydrophobic” covers surface propertiesexhibiting a contact angle of 90 degrees or above. In the presentcontext, however, the expression “hydrophilic” is ascribed to surfaceshaving contact angles less than 30 degrees which surfaces ensure wettingthereof. The expression “hydrophobic” is here ascribed to surfaceshaving contact angles larger than 60 degrees. Other definitions aredefined elsewhere in the description.

3. BRIEF DESCRIPTION OF THE DRAWINGS

In the following, by way of examples only, the invention is furtherdisclosed with detailed description of preferred embodiments. Referenceis made to the drawings in which

FIG. 1 shows an embodiment of lift-off microstructured plasmapolymerised polymers on a substrate according to the invention;

FIG. 2 shows another embodiment of lift-off microstructured plasmapolymerised polymers on a substrate according to the invention;

FIGS. 3A-3D show a preferred embodiment of a method of microstructuringa deposition material on a substrate by a shadow lift-offmicrostructuring;

FIGS. 4A-4F show a preferred embodiment of a method of lift-offmicrostructuring a deposition material on a substrate by the lift-offmethod;

FIGS. 5A-5H show a preferred embodiment of a method of lift-offmicrostructuring a deposition material a substrate using a metalsacrificial layer, plasma polymerisation deposition, and lift-offaccording to the present invention;

FIG. 6 shows a Scanning Electron Microscope (SEM) image of amicrostructured silicon-oxide surface having a microstructure pattern inform of capital letters provided by plasma polymerisation depositionaccording to the present invention;

FIG. 7 a shows a cross-sectional top-view illustration of an electrodearrangement in a plasma deposition apparatus according to an embodimentof the present invention;

FIG. 7 b shows a cross-sectional top-view illustration of anotherelectrode arrangement in a plasma deposition apparatus as shown in FIG.7 a; and

FIGS. 8-11 show CCD-camera images (10× magnification) of bacterialsedimentation test slides having cell adhesive, cell non-adhesive,hydrophilic, or hydrophobic surfaces.

4. DETAILED DESCRIPTION

“Microstructured Devices”

FIG. 1 shows an embodiment of lift-off microstructured plasmapolymerised polymers on a substrate according to the invention.

Surfaces of a lift-off microstructured plasma polymerised polymer on asubstrate silicon chip comprises an 8×8 array of patches ofcell-adhesive surface 102 and cell non-adhesive surface 101 therebetween.

Surfaces of a substrate, here in form of a silicon chip 100, ismicrostructured by a lift-off microstructuring method according to thepresent invention, said method comprising plasma polymerisationdeposition of a base coating prepared by plasma polymerisationdeposition of para-xylene as described in example 1 followed bydeposition of a top coating prepared by plasma polymerisation ofallylamine forming patches 102 of cell-adhesive surfaces. The plasma isprepared as described in example 10 according to the procedureillustrated in FIGS. 4A-4F, repeated twice with alignment there between.The white edges 103 illustrate non-covered substrate.

The non-adhesive surface 101 is prepared by deposition of a base coatingprepared by plasma polymerisation deposition of para-xylene as describedin example 1 followed by deposition of atetra-methylsilane/tri-methylphosphite/Ar-plasma as described in example10 and microstructured by repeated use of the lift-off microstructuringmethod.

Single cells can become affixed and/or positioned to cell-adhesivesurfaces but not to the non-adhesive surfaces that surrounds thepatches, or at least cannot be effectively bound thereto.

FIG. 2 shows another embodiment of lift-off microstructured plasmapolymerised polymers substrate in form of chip 200 according to theinvention, similar to that shown in FIG. 1 but further including patches202 of hydrophilic cell non-adhesive surface surrounding the hydrophiliccell adhesive surfaces 203. The hydrophilic cell non-adhesive patchesare surrounded by a hydrophobic matrix 201. The white edges 203illustrate non-covered substrate.

The hydrophilic cell adhesive surfaces and the hydrophilic cellnon-adhesive patches are prepared by plasma deposition as described forFIG. 1. The hydrophobic surface is prepared by plasma deposition ofpara-xylene as described in example 1. The microstructuring is carriedout according to the procedure illustrated in FIG. 4. Themicro-structured silicon chip 200 comprises a 5×5 array of a hydrophiliccell-adhesive surface 203 surrounded by a hydrophilic cell non-adhesivearea 202 and a hydrophobic surface 201 there between.

“Microstructuring by Shadow Mask Lift-Off Technique”

In a preferred aspect, microstructuring by lithographic fabrication isbased on the shadow mask lift-off technique, said method being improvedaccording to the present invention.

FIG. 3 shows a preferred embodiment of microstructuring of a depositionmaterial on a substrate by a shadow mask lift-off method, said methodcomprising the steps of providing a sacrificial layer, said layer havinga complementary pattern of that desired in the microstructured depositmaterial on the substrate, deposition of the deposition material on thesubstrate cover by said sacrificial layer wherein said deposition ofdeposition material comprises a step of plasma polymerisation depositionaccording to the present invention.

FIG. 3B shows a sacrificial layer, here a so-called shadow mask 302,e.g. in form of a patterned metal film or a cello tape, placed directlyon a substrate 301 (FIG. 3A).

FIG. 3C shows deposition of a deposition material 303, here a polymerdeposited by plasma polymerisation deposition according to an embodimentof the present invention, on said sacrificial layer 302 and substrate301.

Finally, as shown in FIG. 3D, the sacrificial layer 302 with depositeddeposition material 303 is dissolved/etched, lifting off undesired partsof the deposit material and providing a desired microstructure patternof deposited material, here a plasma polymerisation deposition material,on the substrate.

With this technique lower feature size of about 20 μm can be achieved.Although for practical purposes the lower feature size is closer to 50μm.

An advantage of this shadow mask lift-off technique is that it is verysimple, the sacrificial layer being a prepared shadow-mask positioneddirectly on the substrate to have a microstructuring deposit materialdeposited thereon.

Further, application of multiple layers of deposit materials can beachieved by successively repeating the method on the same substrate.

A disadvantage of this shadow mask lift-off technique is that it isdifficult to obtain multiple layers for small feature sizes becauseaccurate alignment of the shadow mask is difficult, or even impossible,for lower feature sizes, e.g. in the range 1-2 μm.

“Microstructuring by Lift-Off Technique”

In a preferred aspect, microstructuring by micro-lithographicfabrication is based on the well-known lift-off technique, employingconventional deposition techniques, see, e.g. S. M. Sze, SemiconductorDevices, Physics and Technology, John Wiley & Sons, 1985, pp. 441-442,said method being further improved according to the present invention.

FIGS. 4A-4F show a preferred embodiment of microstructuring a depositionmaterial on a substrate by the lift-off method, said method comprising:a step of providing a sacrificial material, here a layer of photoresist,on a substrate, said sacrificial layer comprising a complementarypattern of the final microstructured deposited material; a step ofdepositing a deposition material on said deposited sacrificial layer andsubstrate, and a step of lifting off said sacrificial layer covered withdeposited material, said lift-off process leaving deposited material onthe substrate; wherein said step of depositing a deposition materialcomprises a step of plasma polymerisation deposition of amicrostructuring deposition material according to the present invention.

FIG. 4B shows a sacrificial layer in form of a thin UV-sensitivephotoresist 402, here a negative resist typically having a thickness inthe range 1.5-4.2 μm spun onto a substrate 401 (FIG. 4A), here astandard silicon wafer. After a short bake, typically at a temperatureof 90° C. for 30 s on a hotplate (the baking time being adapted to theresist thickness), the photoresist 402 is lithographic exposed toUV-light 404 through a mask 403. The pattern of the mask is therebytransferred to the photoresist as shown in FIG. 4C. The unexposedphotoresist is dissolved/etched in a negative resist process by a resistdeveloper, typically a NaOH solution as shown in FIG. 4D, providing asacrificial layer with a complementary pattern of the microstructure tobe deposited on the substrate. FIG. 4E shows deposition of a depositmaterial 405 on the developed photoresist 402 and substrate 401, heredeposition by plasma polymerisation deposition according to anembodiment of the present invention, as described further andexemplified below.

Finally, as shown in FIG. 4F, the underlying photoresist sacrificiallayer 402 with deposited material 405 is dissolved/etched thereby“lifting off” the undesired deposited material, here plasma depositedpolymer, providing the desired microstructure pattern of depositedmaterial, here a plasma polymerisation deposit.

This chemical lift-off is preferably performed using acetone in anultrasonic bath.

For application of multiple microstructuring polymer layers, the processsequence is simply repeated after precise alignment using dedicatedmicrolithography equipment.

“Lift-Off Microstructuring Using Metal Sacrificial Layer”

In a preferred embodiment of the present invention, the sacrificiallayer is a metal layer.

FIG. 5A-5H show a preferred embodiment of a method of lift-offmicrostructuring a deposition material on a substrate using a metalsacrificial layer, plasma polymerisation deposition, and lift-offaccording to the present invention.

FIGS. 5A-5B show a metal 502 (FIG. 5B), e.g. aluminium, deposited on asubstrate 501 (FIG. 5A), e.g. a silicon wafer, by electron-beamevaporation or sputtering.

FIG. 5C shows a thin UV-sensitive photoresist 503 spun onto the metaldeposit 502 on the substrate. After a short bake, the resist is exposed,here by UV light 505, through a mask 504, see FIG. 5D.

FIGS. 5E-5F show the step of development (FIG. 5E) of the photoresist503 and etching off metal sacrificial layer 502 providing acomplementary pattern (negative) in the metal sacrificial layer; seeFIG. 5F. In FIG. 5G, a plasma polymerisation deposition layer 506, herea polymer, is applied to the patterned metal sacrificial layer.

In FIG. 5H the metal layer 502 with polymer deposit 506 thereon islifted off from the substrate 501.

The photoresist is dissolved in acetone.

Preferable etching agents for aluminium include:

-   (a) phosphoric acid, preferably in a ratio H₂O:H₃PO₄:HNO₃ of 2:16:1    at 50° C.;-   (b) acidic acid, preferably in a ratio H₂O:H₃PO₄:HNO₃:CH₃COOH of    5:76:3:15 at 40° C., or-   (c) NaOH.

The steps of plasma polymerisation deposition and development shown inFIGS. 5G and 5H are equivalent to the steps shown in FIGS. 4E-4F in thelift-off process.

FIG. 6 shows a Scanning Electron Microscope (SEM) image of asilicon-oxide surface having a microstructure pattern in form of capitalletters provided by plasma polymerisation deposition according to thepresent invention.

Plasma polymerised polymers were deposited on the surface of asubstrate. The letters are “written” with alternate hydrophilic 601 andhydrophobic 602 letters. The letters have a height of approximately 35μm and a width of 25 μm; the scale A indicates about 100 μm. Thehydrophilic surfaces were prepared by plasma deposition ofN-vinylpyrrolidone, and the hydrophobic surfaces were prepared by plasmadeposition of para-xylene.

“Lift-Off Microstructuring Apparatus”

Apparatus for carrying out lift-off microstructuring of a depositionmaterial on a substrate according to the present invention comprises aplasma polymerisation deposition apparatus which deposition apparatus isadapted to provide a plasma polymerisation gas of a suitable plasmapower density to preserve a substantial portion of the functional groupsof the monomer gas used in said plasma polymerisation.

In a preferred embodiment, the plasma polymerisation depositionapparatus comprises an electrode system providing an AC, or virtual DCplasma, in a reaction chamber containing a sample holder for a substrateto be treated.

Such an electrode system is disclosed in EP 0 741 404, the content ofwhich is incorporated by reference. Generally, this electrode systemcomprises a number of electrodes connected to various AC voltages ofdifferent voltages, frequencies, and each voltage having voltage phaseshifts with respect to each other. The voltages are in the range50-10.000 volt, preferably 100-2000 volt. The frequencies are in therange 10 to 10.000 Hz, preferably 30 to 200 Hz, in particular 50 or 60Hz. In cases where 3 or more phases are used the phase shifts areselected so that the plasma intensity is substantially constant duringthe various cycles of the voltages for the number of voltages applied.E.g. for n voltages a phase shift of 1/n period is preferred, i.e. forn=3 a phase shift of 360/3 degrees is preferred.

FIG. 7 a shows a cross-sectional illustration of an electrodearrangement in a plasma deposition apparatus according to an embodimentof the present invention.

Three electrodes 710 are arranged in a vacuum chamber 700 to provideplasma in a reaction section thereof for exposure of a substrate to saidplasma. The electrodes are connected to three voltages 709, here threestep-up AC transformers, e.g. CAMP.02533 supplied by Nordelet Tronica,Italy, and further connected to three variable AC transformers 708. Thetransformers can be of any suitable kind e.g. Vario RV31002-20 3x10A0-220V supplied by Lubcke. The reaction section comprises a substrateholder 712 which in a preferred embodiment is supplied with a DCvoltage. During the pre-treatment step the ion bombardment of thesubstrate can be amplified by applying a negative voltage bias to thesubstrate holder. During the top coating deposition the ion bombardmentof the substrate can be reduced by applying a positive voltage bias onthe substrate holder. The substrate holder can be arranged in anysuitable way (not shown) which ensures a sufficiently homogeneous plasmaalong the surface of the substrate.

The vacuum chamber comprises various inlets and outlets (not shown) forsupplying gasses to and from the vacuum chamber, e.g. inlets for processgases such as Ar and H₂, and monomer gasses for plasma polymerisationdeposition according to the invention, and outlets connected to one oremore vacuum pumps for discharge of waste gasses and for sustainingvacuum.

FIG. 7 b shows a cross-sectional illustration of another electrodearrangement in a plasma deposition apparatus as shown in FIG. 7 a.

Such an electrode system is disclosed in WO 00/44207, the content ofwhich is incorporated by reference. Generally, this electrode systemcomprises a number of electrodes arranged along an inner surface 704,here a glass cylinder, of the vacuum chamber so that phase-shiftedvoltages supply pairs of electrodes 7101, 7102. The electrode generatesan inhomogeneous plasma zone 705 and an inner (central) zone ofhomogeneous diffusion plasma. A substrate holder 712 for carrying asubstrate is arranged in the plasma diffusion zone.

2-phase voltages instead of the 3-phase voltage supply shown in FIG. 7 asupply the electrodes.

The vacuum chamber comprises various inlets and outlets (not shown) forsupplying gasses to and from the vacuum chamber similar to thosedescribed for the embodiment shown in FIG. 7 a.

“The Plasma Power Density”

The reactions going on in the plasma strongly depend on the averageplasma power density, ρ_(plasma) which is conveniently defined as theratio of the electrical power over the total plasma gas volume,V_(plasma),ρ_(plasma)=electrical power/V _(plasma)  (1)where the electrical power is given by the product of the measuredvoltage over the electrodes multiplied by the measured current of thepower supply output, and where the gas plasma volume is given by thevolume of the plasma section. Depending on the electrode set-up it canbe difficult to determine the exact boundary of the plasma volume andthereby the total plasma volume. As a rule of thumb the gas inside theplasma volume emits visible light, thus the position of the plasmavolume boundaries can be estimated by observing the plasma from variousangles. However, this is not always practically achievable. In the caseof AC diffusion plasma the total plasma volume to a good approximationis given by the volume encompassed by the outermost electrodes. E.g.,for a cylindrical electrode set-up of radius R and length H, the totalplasma volume, V_(plasma), is given byV _(plasma) =H×π×R ²  (2)

In the following this definition of total plasma volume is used tocalculate average plasma densities in accordance with equation (1).

The average plasma power density, ρ_(plasma), can be accuratelycontrolled by varying the following plasma process parameters: Electrodevoltage, pressure, and gas composition. Within a certain process window200 ρ_(plasma) increases with increasing electrode voltage and increaseswith increasing pressure. The dependence of ρ_(plasma) on the gascomposition is quite complex. However, the presence of easily ionisedand otherwise inert gasses such as the noble gasses ensures theexistence of plasma even at low average power densities such preferredin the present invention. For typical feed gas compositions the processwindow is defined by electrode AC voltages in the range 200-2000 V andpressures in the range 0.01-1 mbar.

For a number of popular electrode geometries approximate values ofV_(plasma) can be calculated in accordance to equation (1) by insertingproper values of H and R. For an inductively coupled plasma with acylindrical coil wound around a cylindrical vacuum container, H is givenby the length of the coil and R is given by the inner radius of vacuumcontainer. For a plasma sustained between two parallel circularelectrodes, H is the distance between the electrodes, and R is theradius of the electrodes.

It should be noted that values for the plasma power density for anygiven plasma section, which geometrical form may deviate from that ofthe cylindrical electrode set-up in equation (2), can be calibratedagainst such a standard plasma section. This can be achieved by opticalemission spectroscopy (OES) measurements of the emitted light from theplasma, since the intensity of the emitted light is quite sensitive tothe plasma power density. For the purpose of calibration pure noble gasplasma is preferred. For any such noble gas a large number of emissionwave lengths are present in the emitted light. However for each noblegas, the intensity of certain wavelengths are dominating and thereforeespecially useful for performing such a calibration, e.g. in the case ofa pure argon plasma the intensity of the optical emission at 434.8 nm isrelatively intense, and for a pure helium plasma the emission at 587.6nm is strong.

5. EXAMPLES

Preferred embodiments of the invention are further illustrated by thefollowing examples.

Example 1 “Lift-Off Microstructuring on Silicon Wafers-Base Coating byPlasma Polymerisation Deposition of p-xylene—Hydrophobic Functionality”

The lift-off microstructuring method steps were conducted as illustratedin FIGS. 4A-4F under the following conditions.

Precise alignment between two or more plasma polymerised polymersurfaces is achieved using lithography equipment and alignment marksformed on the silicon substrate; said equipment being known in the art.

Except for step E, shown in FIG. 4E, the method is conducted followingconventional methodologies, see e.g. “Lithography in ExperimentalEnvironment” by Hovinen, Malinin and Lipsanen, Helsinki University ofTechnology, in Reports in Electron Physics 2000/21, Espoo 2000).

Step A: “Substrate”

Silicon substrates, here standard 4″ silicon wafers (Okmetic Oy) onwhich SiO₂ is grown, were provided.

SiO₂ Growth:

-   Equipment: Tempress system-   Process: Wet oxidation-   Temperature: 1000° C.-   Pressure (H₂O): 760 Torr-   Time: 10 min-   Oxide film thickness: 1000 Å    Step B: “Sacrificial Layer—Photoresist Layer”

A resist was spun on said substrate.

-   Equipment: SSI 150 dual track spinner-   Resist: AZ5214E (Shipley Company, L.L.C)-   Thickness: 4.2 μm-   Dispensed volume: approx. 4 ml    Spin:-   Speed: 700 rpm-   Time: 40 s    Rest:-   Time: 150 s    Bake (Hotplate):-   Temperature: 90° C.-   Time: 120 s.    Step C: “Lithography”    Exposure of Photoresist-   Equipment: Karl Suss MA/BA6 aligner-   Process: Positive resist    Settings:-   Mode: Soft contact-   Alignment gap: 20 μm (Gap between the resist and mask during    alignment for alignment between to polymer surfaces)-   Exposure gap: 0 μm (soft contact between mask and resist during    exposure)-   Exposure time: 16 s-   Lamp power: 300 W-   Wavelength: 365 nm

The mask was a conventional mask prepared according to the principlesdisclosed by S. M. Sze, “Semiconductor Sensors”, John Wiley & Sons,1994, 1^(st) edition, pp. 25-27, here by computer-generated quartz maskphotolithography.

Step D: “Development of Resist”

-   Developer: AZ 351B (Shipley Company, L.L.C) Dilution-   ratio to water: 1:5 (Developer: basic NaOH at pH 14)-   Development time: 2.30 min-   Water rise: 5 min    Step E: “Plasma Polymerisation Deposition”    “Substrate Pre-Treatment”

The surface is first treated with argon so as to clean and possiblyactivate the surface.

The pre-treated 4″ silicon wafers were placed in a 135 litre 2-phaseAC-plasma chamber. The pressure in the chamber was lowered to 0.05 mbarand a flow of 20 sccm argon was led into the chamber. Plasma powerdensity of 5 W/litre was started.

Hydrogen is then provided with the aim of reducing any Si—OH groups onthe surface to Si—H groups so that the subsequently added p-xylene wereable to form Si—C—R bonds with the silicon substrate. Without thereduction with hydrogen, it is believed that base labile Si—O—C—R groupscould have been formed.

After 60 seconds, the flow of argon was lowered to 10 sccm and a flow ofhydrogen (10 sccm) was started.

After another 30 seconds the argon flow stopped.

“Base Coating by Plasma Polymerisation Deposition of p-xylene onDeveloped Resist”

After 60 seconds with hydrogen plasma, the hydrogen flow was stopped, aflow of p-xylene vapour (20 sccm) and a flow of argon (10 sccm) werestarted. The plasma power density was lowered to 3 W/litre.

After 60 seconds with plasma polymerisation of p-xylene, the p-xyleneflow was stopped. The plasma was turned off, all flows were stopped andthe pressure was raised to atmospheric pressure.

Step F: Lift-Off—Chemical/Mechanical

Solvent: Acetone

Ultrasound is used to promote the lift-off.

In other embodiments the lift-off step include mechanical lift-off, ormetal sacrificial layer etching.

This p-xylene base coating provides a hydrophobic functionality to thesurface.

Example 2 “Lift-Off Microstructuring on Silicon Wafers—Top Coating byPlasma Polymerisation Deposition of 1-vinyl-2-pyrrolidone—HydrophilicFunctionality”

Example 1 was repeated except that Step E was modified to include a topcoating by plasma polymerisation deposition of 1-vinyl-2-pyrrolidone asfollows:

A flow of 1-vinyl-2-pyrrolidone (15 sccm) was started after the xyleneflow was stopped. The power was lowered to 0.5 W/litre and the pressurewas raised to 0.1 mbar. The plasma polymerisation of1-vinyl-2-pyrrolidone was continued for 120 seconds. The plasma wasturned off, all flows were stopped and the pressure was raised toatmospheric pressure.

The final layer of poly(vinyl pyrrolidone) provides a hydrophilicfunctionality; primarily supplied by the pyrrolidone group whichrequires a low plasma power density to remain intact during the plasmadeposition.

Example 3 “Lift-Off Microstructuring on Silicon Wafer—Sequential TopCoatings by Plasma Polymerisation Deposition of p-xylene and1-vinyl-2-pyrrolidone—Hydrophobic and Hydrophilic Functionalities”

The process sequence was performed twice in sequence on the same siliconwafer substrate. A hydrophobic pattern and a hydrophilic pattern wereprepared as described in Example 1 and Example 2, respectively.

The procedural steps, repeated twice with alignment there between, areshown in FIG. 5. Letters are “written” with alternating hydrophilic 601and hydrophobic 602 letters. The letters have a height of 35 μm and awidth of 25 μm.

Example 4 “Tests of Glass Substrates—Top Coating by PlasmaPolymerisation Deposition of p-xylene—Contact Angle and AlkalineResistance”

Test coatings of plasma polymerised p-xylene on glass, preparedaccording to example 1, were refluxed in acetone and toluene,respectively, for 24 hours. The contact angle with water wassubsequently measured in order to determine whether the coating was lefton the substrate. All samples showed a contact angle of between 85° and95° (water on glass would give a contact angle of approx. 40°). Themeasured contact angle was substantially equal to the contact anglemeasured before the refluxing.

Similar samples were tested in alkaline environment in solutions ofNaOH. The coatings resisted a solution with pH 12.5 for more than 24hours and a solution with pH 14 for more than 1 hour. It was thereforeconcluded that the coating layers were able to resist even harshconditions as those prevailing in lift-off microstructuring processes.

Example 5 “Glass Substrate—Top Coating by Plasma PolymerisationDeposition of diethyleneglycol-vinylether—Cell Non-AdhesiveFunctionality”

Example 2 was repeated except that glass was used as substrate insteadof SiO₂-grown silicon wafer and that diethyleneglycol-vinylether (DEGVE)was used instead of 1-vinyl-2-pyrrolidone. The microstructured surfacesexhibited a contact angle of 10° and cell non-adhesive properties.

Example 6 “Lift-Off Microstructuring of Silicon Wafer—Top Coating byPlasma Polymerisation Deposition of Tetra-methylsilane andTrimethylphosphide—Hydrophilic and Cell Non-Adhesive CoatingFunctionalities”

A silicon wafer (substrate) was placed in a 30-litre cylindrical plasmachamber equipped with a two-phase electrode system—as described above.Tetramethylsilane (TMS) and trimethylphosphide (TMPP) were use as topcoating monomers.

The substrate was treated in three steps under the following conditions,respectively:

-   1) pre-treatment: Ar plasma at pressure 0.1 mbar, Ar flow 8 sccm, AC    voltage 250 V, and duration 120 s,-   2) base-coating: Ar/H₂ plasma at pressure 0.1 mbar, Ar flow 4 sccm    and H₂ flow 5 sccm, AC voltage 250 V, and duration 300 s,-   3) top-coating: Ar/TMS/TMPP/air plasma at pressure 0.1 mbar, Ar flow    4 sccm, TMS flow 5 sccm, TMPP flow 5 sccm, and air flow 3 sccm, AC    voltage 250V, and duration 300 s.

An IR spectrum of the coating on the NaCl crystal was recorded, showingabsorption bands at 961 cm⁻¹ (P—O, Si—O or Si—H) and 1070 cm⁻¹ (Si—O),1165 cm⁻¹ (P═O), 1445 cm⁻¹ (CH₂), 1647 cm⁻¹ (C═C and P—OH), 2855 cm⁻¹(CH₂), 3200 cm⁻¹ (OH), 3400 cm⁻¹ (OH).

The static contact angle of demineralized water with the coated siliconwafer was measured to be 18.6 degrees with a standard deviation of 2.2.

“Test of Cell Adhesive Functionality”

Cell adhesive and/or non-adhesive properties of plasma polymerisedsurfaces were tested by bacterial sedimenttation thereon.

Two square pieces, samples, of approximately 1 cm² were cut from thewafer and tested independently in the following way:

The surface of the sample was exposed to a bacterial culture (E. Colik-12) which previously had been washed with ice-cold water andresuspended into ice-cold phosphate buffer saline (PBS). The bacteriasuspension was allowed to sediment onto the surface for one hour beforea gentle flow (1 ml/min) of PBS was induced over the surface to removeunattached bacteria.

Finally the samples were investigated with a microscope using anobjective with 10 times magnification. Images were recorded with the useof a CCD camera. The images are shown in FIG. 8 and FIG. 9 (width 0.7mm, height 0.5 mm).

FIG. 8 shows a sample for which no cell sedimentation can be observedwhereas FIG. 9 shows a sample for which single cells sediments (brightspots) are scattered across the surface.

In conclusion, a silicon wafer with a hydrophilic and cell non-adhesivecoating was successfully produced.

Example 7 “Silicon Wafer—Top Coating by Plasma Polymerisation Depositionof Difluoroethylene—Hydrophobic and Cell Adhesive Functionalities”

A highly fluorinated polymer is generally known to have hydrophobicproperties. In this example, a hydrocarbon base coating was deposited ona silicon wafer (substrate) by plasma polymerisation of hexene asmonomer. On this base coating a fluorinated top coating was deposited byplasma polymerisation of difluoroethylene as monomer.

The substrate was placed in the plasma chamber described in the aboveexample.

As an initiation step, a flow of 2.5 sccm Ar was established and theplasma was ignited at 1200 V. After 1 minute, 20 sccm hexene was addedto the gas flow and the voltage was lowered to 1000 V. At theseconditions the plasma was maintained for 1 minute. The hexene flow wasthen stopped, and a difluoroethylene flow of 38.4 sccm was started.After ten minutes the plasma was ignited at 700 V and the top coatingwas deposited with a flow of 2.5 sccm Ar and 38.4 sccm difluoroethylenefor 2 minutes.

The static contact angle with demineralised water was measured to be67.4 degrees, with a 0.9 standard deviation.

The FT-IR spectrum was recorded of the top coating, showing absorptionbands at 881 cm⁻¹ (Si—F), 1350-1120 cm⁻¹ (C—F), 1440 cm⁻¹ (CH₂),1650-1700 cm⁻¹ (C═C or C—F), 2957 cm⁻¹ (CH₂).

The cell adhesive properties were tested by the test of cell adhesivefunctionality. The results for the two samples are shown in FIG. 10 andFIG. 11, respectively. The number of cells per area is clearly higherfor this surface than for the surface described in example 6.

In conclusion a silicon wafer could successfully be provided ahydrophobic functionality and a moderately cell adhesive functionality.

Example 8 “Glass Slides—Top Coating by Plasma Polymerisation Depositionof Carboxylic Acid Anhydride”

Substrates, here 10 microscope glass slides pre-treated according to thesubstrate pre-treatment procedure described above, of length 7.62 cm (3inch), width 2.53 cm (1 inch), and thickness 1 mm, were placed in asubstrate holder which was then placed a 300 litres cylindrical plasmachamber equipped with a two-phase electrode system (135 litres).

In this embodiment, substrates were treated on one side only by coveringthe other sides with a cover substrate; here a microscope glass slidessimilar to the deposition substrate. Each substrate was placed on asupporting slide of same dimensions before being placed in the chamber.

The 10 pairs of supports and substrates were evenly distributed on asubstrate holder, here a tray, comprising a stainless steel gridelectrically isolated from the electrodes.

A rectangular calibration NaCl crystal was placed on a supporting slidein the middle of the chamber.

The glass slides, and the calibration crystal, were subjected to threeconsecutive gas treatments providing a polystyrene base coating:

-   Ar-plasma pre-treatment: exposure to an Ar-plasma at pressure 0.025    mbar, said plasma being provided by an argon flow of 25 sccm, a    plasma power density of 3 Watt/litre, and had a duration of 60 s.-   Ar/H₂-plasma pre-treatment: exposure to an Ar/H₂-plasma at pressure    0.025 mbar, said plasma being provided by an argon flow of 17 sccm,    H₂-flow of 7 sccm, a plasma power density 3 Watt/litre, and had a    duration of 60 s,-   polystyrene base coating: exposure to a styrene/Ar-plasma at a    pressure of 0.075 mbar, said base coating plasma being provided by a    styrene flow of 80 sccm, an argon flow of 40 sccm, and a plasma    power density of 2 Watt/litre, and had a duration of 120 seconds.

The FT-IR spectrum was recorded of the base coating, showing absorptionbands at 3056 and 3025 cm⁻¹ (aromatic C—H), 2800-2900 cm⁻¹ (—CH₂—,—CH₃), 1601 cm⁻¹ (aromatic C—C) 1451 cm⁻¹ (—CH₂—), 1373 cm⁻¹ (—CH₃).

Ten pressure-sensitive tape masks were prepared: A pressure sensitiveadhesive tape (PSA) was prepared by evenly spreading 20 ml of a solutionconsisting of 18 g of thermoplastic elastomer, Kraton KX601 supplied byShell Chemicals, and 5 grams of tackifying resin, Arkon P15 supplied byArkava, dissolved in 250 ml of xylene, over a piece of thin writingpaper (30 cm long and 21 cm wide) and letting the xylene evaporate. Fromthe resulting PSA sheet 10 rectangular pieces of microscope slide formatwere punched. The punch was designed such that 24 holes of diameter 3 mmwere produced in the paper. The holes were arranged in 3 rows of 8circular holes, neighbouring holes being 3 mm apart.

Each of the polystyrene base coated slides were covered on one side byone such PSA mask and transferred to the plasma chamber together withthe calibration crystal.

A methacrylic acid anhydride (MAAH) top coating was deposited byexposure to a plasma at a pressure of 0.3 mbar, said top-coating plasmabeing provided by bobbling argon through liquid MAAH at a flow of 5 sccmand feeding the MAAH/Ar-gas mixture to the plasma chamber, a plasmapower density of 1.5 Watt/litre, and had a duration of 300 s. After theplasma treatment the PSA masks were removed by hand.

Characterisation of the Product:

A plasma treated slide was briefly submerged in demineralised water andthen kept in a vertical position. Water was observed to de-wett in areasof the slide covered by the mask, whereas water remained in the circularspots generated by exposure to the MAAH/Ar-plasma.

The chemical structure of the coating was analysed by infraredspectroscopy of the coated NaCl-calibration crystal.

Additional FT-IR absorption peaks were observed at 3100-3600 cm⁻¹ (O—H),1772-1800 cm⁻¹ (acid anhydride C═O), 1130 cm⁻¹ (acid anhydride C-0).

In result, a chemically structured surface was produced withwell-defined hydrophilic spots in a hydrophobic matrix.

Example 10 “Plasma Polymerisation Deposition Of Allylamine”

A silicon wafer, substrate, was placed on a tray in a plasma apparatus.The apparatus comprising a 30 litres cylindrical plasma chamber equippedwith a two-phase cylindrical electrode system of volume 3 litres.

The electrodes were connected to a two-phase 50 Hz AC-power supply witha manually tuneable voltage. A rectangular NaCl crystal was placed nextto the substrate on the tray.

The substrate, and the NaCl crystal, was subjected to three consecutivegas treatments providing a base coating and a top coating:

-   the pre-treatment: exposure to an Ar-plasma at a pressure of 0.07    mbar, said plasma being provided by an argon flow of 25 sccm, and an    AC voltage 1200 V of 50 cycles per second, and had a duration of 60    s, and-   the base coating: exposure to a hexene/Ar-plasma at a pressure 0.1    mbar, said top-coating plasma being provided by an hexene flow of 20    sccm, an Ar-flow of 2.5 sccm, and an AC voltage of 1000 V of 50    cycles per second, and had duration 60 s.-   the top coating: exposure to an allylamine/Ar-plasma at a pressure    0.2 mbar, said top-coating plasma being provided by an allylamine    flow of 30 sccm, an Ar-flow of 2.5 sccm, and an AC voltage of 700 V    of 50 cycles per second, and had a duration 120 s.

Placing a droplet of demineralised water on a substrate coated asdescribed above and observing the contact angle with water tested theaffinity of the coating towards water. Typical contact angles were about50 degrees.

The chemical structure of the coating was analysed by infraredspectroscopy of the coated NaCl-calibration crystal.

The following absorption peaks were observed: 3370 cm⁻¹ (primary amine),2800-2900 cm⁻¹ (—CH₂—, —CH₃), 2206 cm⁻¹ (nitrile), 1629 cm⁻¹ (primaryamine), 1452 cm⁻¹ (—CH₂—), 1375 cm⁻¹ (—CH₃).

In conclusion a silicon wafer with a hydrophilic amine rich coating wasproduced.

1-41. (canceled)
 42. A process of lift-off microstructuring of a polymeron a substrate, said process comprising the steps of: (a) providing thesubstrate having a sacrificial layer in a predetermined micro-pattern;(b) depositing a polymer layer on the sacrificial layer/substrate; and(c) dissolving/etching the underlying sacrificial layer (lift-off),characterized in that the polymer layer is constituted by a cross-linkedpolymeric material prepared by plasma polymerization of a monomer gas ina plasma, said monomer gas comprising one or more types of substitutedbenzenes.
 43. The process according to claim 42 wherein the polymerlayer is functionalised prior to dissolution of the underlying layer.44. The process according to claim 42 said process comprising the stepsof: (a) spinning a UV-sensitive photoresist on the substrate; (b)masking the resist with a predetermined pattern and exposing the resistto UV light through the mask; (c) developing the resist; (d) depositinga polymer layer on the resist/substrate; and (e) dissolving theunderlying UV-sensitive photoresist (lift-off).
 45. A process accordingto claim 42 wherein the one or more types of monomers are selected fromsubstituted benzenes.
 46. The process according to claim 45 wherein thesubstituted benzene has the general formula:Ar(R^(n))_(n) wherein Ar is a benzene ring, n is 1-6, and R^(n) is nsubstituents (R¹, R², R³, R⁴, R⁵, R⁶) covalently bound to the benzenering, the substituents (R¹, R², R³, R⁴, R⁵, R⁶) being independentlyselected from C₁₋₆-alkyl, C₁₋₆-alkenyl, C₁₋₆-alkynyl, C₁₋₆-alkoxy,C₁₋₆-alkylcarbonyl, C₁₋₆-alkylcarbonyl, C₁₋₆-alkoxycarbonyl, carbamoyl,mono- and di(C₁₋₆-alkyl)aminocarbonyl, formyl, hydroxy, carboxy,carbamido, thiolo, nitro, cyano, nitro, amino, mono- anddi(C₁₋₆-alkyl)amino, and halogen (fluoro, chloro, iodo, bromo), whereinthe C₁₋₆-alkyl, C₁₋₆-alkenyl, C₁₋₆-alkynyl and C₁₋₆-alkoxy groups in theabove may be substituted with substituents selected from hydroxy,C₁₋₆-alkoxy, carboxy, amino, mono- and di(C₁₋₆-alkyl)amino and halogen.47. The process according to claim 45 wherein less than 10% of thedouble bonds originating from the substituted benzene are left in thematerial.
 48. A process according to claim 42 wherein the substitutedbenzene monomer or monomers constitute(s) at least 5% of the monomergas.
 49. A process according to claim 42 wherein said a sacrificiallayer (302) on the substrate (301) comprises a mask with a complementarypattern of holes, said pattern corresponding to that of themicrostructure to be deposited on the substrate, said holes beingadapted to expose corresponding parts of the substrate and adapted toreceive deposition material.
 50. A process according to claim 42 whereinthe process steps are repeated two or more times.
 51. A substrateprepared according to the process defined in claim
 42. 52. A devicecomprising a micro-patterned structure said device comprising asubstrate and a plurality of patches and/or areas comprising across-linked material prepared according to the process defined in claim42.
 53. The device according to claim 52 wherein the plurality ofpatches comprising the cross-linked material represent any of thefollowing combinations of surface properties: (i) a subset of thepatches and/or areas having a cell-adhesive surface and a subset of thepatches and/or areas having a hydrophobic surface; (ii) a subset of thepatches and/or areas having a cell non-adhesive surface and a subset ofthe patches and/or areas having a hydrophobic surface; (iii) a subset ofthe patches and/or areas having a cell-adhesive surface and a subset ofthe patches and/or areas having a hydrophilic surface; or (iv) a subsetof the patches and/or areas having a cell-non-adhesive surface and asubset of the patches and/or areas having a hydrophilic surface.
 54. Aprocess of lift-off microstructuring of a polymer on a substrate, saidprocess comprising the steps of: (a) providing the substrate having asacrificial layer in a predetermined micro-pattern; (b) depositing apolymer layer on the sacrificial layer/substrate; and (c)dissolving/etching the underlying sacrificial layer (lift-off),characterised in that the polymer layer is constituted by a cross-linkedpolymeric material prepared by plasma polymerisation of a monomer gas ina plasma, said monomer gas comprising one or more types of(halo)aliphatic compounds of the general formula C_(z)H_(y)X_(x) whereinX is fluoro, chloro, bromo or iodo, z is 1-16 and x+y is 2z+2, 2z, 2z-2or 2z-4; with the proviso that said (halo)aliphatic compounds are notCF₄, C₂F₆, or C₃F₈ when said monomer gas is a gas mixture with H₂; andnot CHF₃.
 55. The process according to claim 54 wherein the polymerlayer is functionalised prior to dissolution of the underlying layer.56. The process according to claim 54 said process comprising the stepsof: (a) spinning a UV-sensitive photoresist on the substrate; (b)masking the resist with a predetermined pattern and exposing the resistto UV light through the mask; (c) developing the resist; (d) depositinga polymer layer on the resist/substrate; and (e) dissolving theunderlying UV-sensitive photoresist (lift-off).
 57. A process accordingto claim 54 wherein said a sacrificial layer (302) on the substrate(301) comprises a mask with a complementary pattern of holes, saidpattern corresponding to that of the microstructure to be deposited onthe substrate, said holes being adapted to expose corresponding parts ofthe substrate and adapted to receive deposition material.
 58. A processaccording to claim 54 wherein the process steps are repeated two or moretimes.
 59. A substrate prepared according to the process defined inclaim
 54. 60. A device comprising a micro-patterned structure saiddevice comprising a substrate and a plurality of patches and/or areascomprising a cross-linked material prepared according to the processdefined in claim
 54. 61. The device according to claim 60 wherein theplurality of patches comprising the cross-linked material represent anyof the following combinations of surface properties: (i) a subset of thepatches and/or areas having a cell-adhesive surface and a subset of thepatches and/or areas having a hydrophobic surface; (ii) a subset of thepatches and/or areas having a cell non-adhesive surface and a subset ofthe patches and/or areas having a hydrophobic surface; (iii) a subset ofthe patches and/or areas having a cell-adhesive surface and a subset ofthe patches and/or areas having a hydrophilic surface; or (iv) a subsetof the patches and/or areas having a cell-non-adhesive surface and asubset of the patches and/or areas having a hydrophilic surface.
 62. Amethod of lift-off microstructuring of a polymer on a substrate, saidprocess comprising the steps of: (a) providing the substrate having asacrificial layer in a predetermined micro-pattern; (b) depositing apolymer layer on the sacrificial layer/substrate; and (c)dissolving/etching the underlying sacrificial layer (lift-off),characterised in that the polymer layer is constituted by a cross-linkedpolymeric material prepared by plasma polymerisation of a monomer gas ina plasma, said monomer gas comprising one or more types of monomersselected from: vinyls, substituted vinyls, acrylics, silanes, andphosphites, or a combination thereof.
 63. The method according to claim62 wherein said acrylic monomer is selected from: acrylic acid,methylmethacrylate, acrolein, acryloylchloride, acrylonitrile.
 64. Themethod according to claim 62 wherein said vinylic monomer is selectedfrom: ethylene, propylene, styrene, N-vinylpyrrolidone.
 65. The methodaccording to claim 62 wherein said substituted vinylic monomer isselected from: vinyl-di-fluoride, hexafluoropropane, vinylchloride. 66.The method according to claim 62 wherein said silane monomer is selectedfrom: tetramethylsilane, hexamethyl-di-silane, tri-methylchlorosilane.67. The method according to claim 62 wherein said silane tri-phosphiteis selected from: tri-methyl-phosphite, tri-ethyl-phosphite.
 68. Amethod according to claim 62 wherein the polymer layer is functionalisedprior to dissolution of the underlying layer.
 69. A method according toclaim 62 wherein said process comprising the steps of: (a) spinning aUV-sensitive photoresist on the substrate; (b) masking the resist with apredetermined pattern and exposing the resist to UV light through themask (c) developing the resist; (d) depositing a polymer layer on theresist/substrate; and (e) dissolving the underlying UV-sensitivephotoresist (lift-off).
 70. A method according to claim 62 wherein saida sacrificial layer (302) on the substrate (301) comprises a mask with acomplementary pattern of holes, said pattern corresponding to that ofthe microstructure to be deposited on the substrate, said holes beingadapted to expose corresponding parts of the substrate and adapted toreceive deposition material.
 71. A method according to claim 62 whereinthe process steps are repeated two or more times.
 72. A substrateprepared according to the method defined in claim
 62. 73. A devicecomprising a micro-patterned structure said device comprising asubstrate and a plurality of patches and/or areas comprising across-linked material prepared according to the method defined in claim62.
 74. The device according to claim 73 wherein the plurality ofpatches comprising the cross-linked material represent any of thefollowing combinations of surface properties: (i) a subset of thepatches and/or areas having a cell-adhesive surface and a subset of thepatches and/or areas having a hydrophobic surface; (ii) a subset of thepatches and/or areas having a cell non-adhesive surface and a subset ofthe patches and/or areas having a hydrophobic surface; (iii) a subset ofthe patches and/or areas having a cell-adhesive surface and a subset ofthe patches and/or areas having a hydrophilic surface; or (iv) a subsetof the patches and/or areas having a cell-non-adhesive surface and asubset of the patches and/or areas having a hydrophilic surface.
 75. Amethod of lift-off micro-structuring a deposition of material on asubstrate, the method comprising: (a) providing the substrate (401), thesubstrate comprising a sacrificial layer (402) thereon, said sacrificiallayer having a predetermined micro-pattern; (b) depositing thedeposition material (405) on the substrate and said sacrificial layer;and (c) dissolving/etching said sacrificial layer, wherein saiddeposition material is a polymer, said polymer comprising a cross-linkedpolymeric material prepared by plasma polymerisation of a monomer gas ina plasma, said plasma being generated by a multiple phase AC supply(708,709,710), or a DC supply.
 76. The method according to claim 75wherein said multiple phase AC supply is two-phase or three-phase ACsupply.
 77. The method according to claim 75 wherein said multiple twoor three phase AC supply generates plasma having plasma power density upto 15 W/l.
 78. The method according to claim 75 wherein said multipletwo or three phase AC supply generates plasma having plasma powerdensity in the range 0.010 to 10 W/l.
 79. The method according to claim75 wherein said multiple two or three phase AC supply generates plasmahaving plasma power density in the range 0.010 to 5 W/l.
 80. A methodaccording to claim 75 wherein said plasma is provided in a reactionchamber having a pressure in the range 10-1000 μbar.
 81. A methodaccording to claim 75 wherein said plasma is provided in a reactionchamber having a pressure in the range 25-500 μbar.
 82. A methodaccording to claim 75 wherein said monomer gas comprises one or moretypes of monomers, and a supply of inert gas.
 83. A method according toclaim 75 wherein said monomer gas comprises one or more types ofmonomers selected from: (i) substituted benzenes, and (ii)(halo)aliphatic compounds of the general formula C_(z)H_(y)X_(x) whereinX is fluoro, chloro, bromo or iodo, z is 1-16 and x+y is 2z+2, 2z, 2z-2or 2z-4; or (iii) a combination there of.
 84. A method according toclaim 75 wherein said monomer gas comprises one or more types ofmonomers selected from: vinyls, substituted vinyls, acrylics, silanes,and phosphites, or a combination thereof.
 85. The method according toclaim 84 wherein said acrylic monomer is selected from: acrylic acid,methylmethacrylate, acrolein, acryloylchloride, acrylonitrile.
 86. Themethod according to claim 84 wherein said vinylic monomer is selectedfrom: ethylene, propylene, styrene, N-vinylpyrrolidone.
 87. The methodaccording to claim 84 wherein said substituted vinylic monomer isselected from: vinyl-di-fluoride, hexafluoropropane, vinylchloride. 88.The method according to claim 84 wherein said silane monomer is selectedfrom: tetramethylsilane, hexamethyl-di-silane, tri-methylchlorosilane.89. The method according to claim 84 wherein said silane tri-phosphiteis selected from: tri-methyl-phosphite, tri-ethyl-phosphite.
 90. Amethod according to claim 75 wherein the method steps are repeated twoor more times.
 91. A substrate prepared according to the method definedin claim
 75. 92. A device comprising a micro-patterned structure saiddevice comprising a substrate and a plurality of patches and/or areascomprising a cross-linked material prepared according to the methoddefined in claim
 75. 93. The device according to claim 92 wherein theplurality of patches comprising the cross-linked material represent anyof the following combinations of surface properties: (i) a subset of thepatches and/or areas having a cell-adhesive surface and a subset of thepatches and/or areas having a hydrophobic surface; (ii) a subset of thepatches and/or areas having a cell non-adhesive surface and a subset ofthe patches and/or areas having a hydrophobic surface; (iii) a subset ofthe patches and/or areas having a cell-adhesive surface and a subset ofthe patches and/or areas having a hydrophilic surface; or (iv) a subsetof the patches and/or areas having a cell-non-adhesive surface and asubset of the patches and/or areas having a hydrophilic surface.